The present invention relates to a process and device for manufacturing plasterboard and more particularly plasterboard with a gypsum core the density of which varies as a function of the distance in relation to the surface. In order to lighten the plasterboard, a known technique is to make plasterboard with a low density core layer by introducing foaming agents into the slurry. This core layer is flanked by high density surface layers. The surface layers of gypsum form one piece with the cardboard sheets. Moreover, the surface layers have a low volume of gas bubbles. The adhesion of this slurry to the cardboard sheet is therefore improved. The surface layers also increase the hardness and rigidity of the plasterboard.
There is therefore a need for a process and a device for manufacturing plasterboard with a core layer presenting a given density and two surface layers the density of which is higher than that of the core layer. Moreover, there is a need for a process and a device for manufacturing this type of board that enables the quantities of additives and foaming agents to be reduced, rejects during the drying stage to be reduced, the bond between the plaster and the cardboard sheets to be improved and which also favours production control and increases the availability of the manufacturing unit.